Metal-to-metal sealing surfaces have been proposed to seal junctions between tubular members such as: blowout preventers, production trees, side outlet valves and wellhead housings. Metal-to-metal seals must be precisely manufactured to enable a seal upon contact of the polished sealing surfaces.
Metal-to-metal seals will not effectively seal if one of the sealing surfaces becomes damaged. This is particularly problematic for inaccessible applications, such as subsea wellheads, where the seal surface cannot be easily removed to refinish the damaged seal surface. Thus, secondary sealing surfaces have been developed for use when a primary surface becomes damaged, for example, see U.S. Pat. No. 5,039,140 and U.S. Pat. No. 5,103,915, both of which are incorporated herein by reference.
However, such proposals are difficult to implement due to the difficulty in maintaining a tolerance in locating the secondary seal surface or in energization of the secondary seal. Further, no prior secondary seal for such an application has provided for a dual metal-to-metal seal, which is desirable for safety reasons. It is an object of the present invention to reduce or eliminate the above-mentioned problems.